I wrote a mini JsDTD (unfinished) last year:

http://alexle.net/experiments/jsdtd/

(code is at http://github.com/sr3d/JsDTD).

I didn't use canvas, just straight HTML.

Side story: I went to an interview at Zynga and demo'ed it. I think I was able to impress the guys there, one of them even thought it was done in Flash. It was just Chrome runs everything so fast. (I got an offer from them but ultimately decided to not take it :) In my opinion, it's definitely a good strategy to build some thing cool, then mention it at the end of a job interview like "by the way, this is what I built". It worked for me.